Rocker arm mechanism



Dec. 5, 1933. N. E. WOOLMAN 1,937,932

ROCKER ARM MECHANISM Filed Oct. 10, 1928 3 Sheets-Sheet 1 M450 5 WOO/ma? INVEN TOR.

' A TTORNE YS.

DGC. 5, 1933. N M N 1,937,932

ROCKER ARM MECHANI SM Filed Oct. 10, 1928 3 Sheets-Sheet 2 7 7 WYZ/ E w- W A e/9o n E. VVaa/mal? I N VEN TOR BY ZZd/vw 'A TTORNE YS.

. 5, 1933. N. E. WOOLMAN ROCKER ARM-MECHANISM Filed Oct. 10, 1928 3 Sheets-Sheet 3 fi/90/7 E l l oo/mafl IN VEN TOR.

A TTORNE YS.

Patented Dec. 5, 1933 1,937,932 ROCKER ARM MECHANISM Nelson E. Woolman, Hermosa, Calif., assignor, by

direct and mesne assignments, to General Motors Research Corporation Application October 10, 1928. Serial No. 311,534

Claims. ((31. 123-90) This invention relates to internal combustion engines, and. particularly to the valve mechanism used in connection with such engines.

In such engines, it is now common to provide l a pair of valves for each cylinder; one for the intake of the gaseous or vaporous fuel, and one for the exhaust. Where overhead valves are used, it is also common to provide a rocker arm for each valve, one end of 'the arm being me- 10 chanically actuated by the cam shaft, and the other endactuating the valve stem so as to depress it against the closing action of a stili valve spring. 1

It is one of the objects of my invention to pro- 18 vide an improved rockerarm mechanism for the valves, whereby smoothness of operation is secured. i V

In the usual valve mechanism, the rocker arm is so arranged that whengthe engine is cold, zo-there is a slight clearance between the rocker arm, and the end of the valve stem. This is necessary in order to ensure that the valve is allowed to seat; and also to take care of' the expension of the parts due to rise in temperature. The adjustment of the clearance is always a delicate process; and it is likelythat annoying clicking of the valve stemwill be maintained throughout the operation of the engine. Besides beingan annoyance, there is always the likelicorrect due to improper adjustments.

"It, is thus another object of my invention to provide a rocker arm device that automatically adjusts itself to the valve stem and the cam mechanism, whereby all clearances at all times are obviated.

I accomplish this result by providing a rocker arm theaxis of which is not definitely fixed, but is rather so arranged that it can be moved slightly against a slow acting bufier or damper, such as a fluid cylinder. It is thus another objectof my invention to provide a floating axis for a rocker arm; which axis is so controlled that the transmission of the force used to open rocker arm axis acts as a fulcrum in spite of its slight freedom of movement. 1

My invention possesses manyother advan-.

hood that the operation of the valve will be in the valve can nevertheless take place. The

general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the taken along planes 2-2 and 3--3 of Fig. 1;

Fig. 4 is a side elevation, in reduced scale, of my device shown in combination with a cylinder head; taken in the direction of arrow 4.

Fig. 5 is an enlarged sectional view of a modified'form of my device, shown as supported on a cylinder head;

Fig. 6 is a side view, in reduced scale, of the device shown in Fig. 5, taken in the direction of arrow 6;

Figs. 7 and 8 are detail sections, taken respectively along planes 7-7 and 88 of Fig. 5;

Fig. 9 is an enlarged sectional view of a still further modification of my invention;

Fig. 10 is a side view, in a reduced scale, of the device shown in Fig. 9, and taken in the direction of arrow 10.

Figure 11 is a top plan view of an engine equipped with the valve mechanism of Figures 5 to 8.

In the form of my invention shown in Figs. 1

to 4 inclusive, a cylinder head 11 is indicated in a more or less diagrammatic manner. I show a valve 12 in the head, arranged to be urged by a strong spring 13 to closed position, interrupting communication from the cylinder to a passage 14, which may lead either to an intakeor exhaust manifold or passageway. It is of'course to be understood that valve 12 exemplifies one of a plurality of exhaust and intake valves, and that the rocker arm structure that will be later described can be indiscriminately applied to all of the valves, whether intake or exhaust.

Valve 12 has a stem 15 that extends out of head 11, and that can be depressed against the action of spring 13 to open it. In order so to open the valve 12, there is provided a rocker arm 16, arranged to be oscillated about a central point, such as the center line or axis of an intermediate boss or hub 17. This axis, as will be hereinafter described, is permitted slight movement. 1

The rocking action of rocker 16 is provided by the action of a push rod 18 that is pushed outwardly in proper cyclical sequence by a cam shaft 19, in a well understood manner. This push rod is shown in the present instance as formed with a socket 20 at its upper extremity, into which fits a ball 21 adjustably carried by the extremity of arm 16.

The opposite end of arm 16 is provided with a pad 22 arranged to engage valve stem 15. Assuming for the present that the axis of boss 17 is stationary, it is evident that an upward movement of rod 18 causes a corresponding depression of stem 15, against the resistance of spring 13, and valve 12 opens.

In order to be sure that the rocker arm 16 will be in continuous contact with both push rod 18 and valve stem 15, I arrange matters in such a way that a resilient force acts downwardly directly above the axis of boss 1'7, thus urging the entire rocker arm 16 downwardly. This force is such that it cannot overcome that of spring 13. Furthermore, as rod 18 actuates the rocker arm 16, a resistance is placed against upward movement of the axis of the arm, whichis much greater than the resilient force urging the arm downward. Thus it is assured that the upward movement of rod 18 will cause only a very small. movement of the axis of rocker arm 16, and that it will cause a corresponding full movement of the pad 22. In other words, the axis of rocker arm 16 is maintained substantially, but not quite, stationary. The manner in which this is accomplished will now be described.

Straddling the boss 17 is a member 23, having a bifurcated saddle portion 24, which extends over the arm 16. This member is guided for vertical movement, by telescoping movement with a stationary guide 25, and is urged downwardly as by a spring 26 interposed between the telescoping parts. In the present form of my invention, member 23 can form a cylindenand guide 25 can form a piston, although this arrangement may readily be reversed, as shown for example in the modifications to be hereinafter described.

Piston 25 is supported on a bracket bar 27, in turn held above the head 11 as by one or more studs 28. Thus piston 25' has a reduced portion 29 forming a shoulder engaging the lower surface of bracket 27. The protruding extremity of portion 29 is threaded, upon which portion a threaded cap 30 is located. Piston 29 is hollow for a purpose now to be described.

It is of course desirable that the downward force on rocker arm 16 be applied without restraint; but there should be a strong resistance against upward movement, in order to ensure that the valve 12 can be operated when an upward force is applied by rod 18. If no great resistance would be opposed to this upward movement, then the arm 16 may act about a fulcrum adjacent pad 22, and movement of push rod 18 would be translated mainly as an upward movement of member 23.

To obviate such an effect, I interpose a dash pot efifect between the cylinder 23 and piston 25. The space 32 between the bottom of piston 25 and the end of cylinder 23 can be filled with a fluid such asoil, and which can escape only slowly from that space as an upward force is exerted on cylinder 23. For this purpose, piston 25 is so arranged that it leaves a free passageway for oil to enter the space 32 when the cylinder makes its suction stroke; that is, when it is moving downward. Thus a plug 33 is held centrally in the hollow space 31 of the piston, which has a passageway 34 and cross passageway 35, through which fluid can enter from above plug 33 down into space 32. In order to keep fluid or oil from escaping between the cylinder 25 and piston 23, a packing ring 36 and a metallic follow-up ring 3'? are interposed between spring 26 and piston 25.

The passage 34 is controlled by a closure or valve 38 urged to closing position by a spring 33. This spring has a large base, resting on ring 37, and a small end that urges valve 38 upwardly. The large base serves to hold the spring in centered position. Upon downward movement of cylinder 23, enough suction is created in space 32 to unseat valve 38, and therefore oil can readily pass into this space. However, when rod 18 moves upwardly, causing an upward force to be exerted on cylinder 23, this valve 38 is held strongly in place, and oil or other fluid cannot escape through passage 34. Valve 38 is shown as guided in its movement by the surface of space 31, so as to provide for accurate action of the valve.

Although iluid' cannot flow out of space .32 through passage 34, there is provided a very narrow space 40 between'plug 33 and piston 25, which is of the order of a fraction of a thousandth part of an inch. As the oil or other fluid is compressed in space 32, it is very slowly forced through the space 40 and into the storage space 31. Thus the upward movement of cylinder 23 is materially resisted. In order that valve 38 shall not cover this space 40, it is made noncircular, as indicated in Fig. 2, although having large surfaces in contact with the inner wall of piston 25' for guiding the valve. I also preferably flare the free end of cylinder 23, as shown at 41, to provide an annular space 42 into which fluid can be placed to replenish the fluid in the cylinder. This fluid can find its way through the radial passageways 43 into space 31, and can in fact act as a supplementaryreservoir. A guide pin 81 can be provided for the cylinder 23, to prevent it turning about piston 25.

It has been found that for most satisfactory results, the size of the escape passage 40 must be very nicely determined. Otherwise the cylinder 23. may act too freely or .too sluggishly on upward movement. One of the important features of my invention resides in the manner in which this passage 40 can-be accurately adjusted.

For this purpose, space 31 is tapered downwardly, and plug 33 is correspondingly tapered. It is apparent then that relative axial movement of the plug 33 with respect to piston 25 will serve to vary the size of the annular passageway; and if the taper is slight as shown, a considerable axial movement is required to produce a small variation. Thus it is easy to set the size accurately. For adjusting the plug position, it is provided in this instance with an integral stud 44 threaded through cap 30. and provided with a slot 45 for rotation with a screw driver. A look nut 46 maintains the plug 33 in adjusted position. The movement of the cylinder 23 is also limited positively, by the space between its free end and the bottom of support 27.

The taper of plug 33 is purposely made toward the inner end so that the hydraulic pressure against it can have no tendency to close the annular passageway 40. 1

The operation of the device is apparent from the foregoing. Spring 26 can always act rapidly to keep the rocker arm 16 always in contact with stem 15 and rod 18, although it is too weak to compress the valve spring 13. On the contrary,

when push rod 18 operates, the axis of rocking for arm16 is permitted to move upwardly only slightly, as there is. much more resistance to. the compression of the fluid in space 32. tha n1 to the compression of spring 13. By proper adjustment of plug 33', this resistance of thefiuid can be so adjusted that: the total upwardmovementof the cylinder 23 is very slight for a corresponding full opening of: valve 12.

Itis not essential" for the purposes of this invention,ctolocate thespring 26 in the cylinder 23. 'Anexternal setof' springscan be provided. Thus in the embodiment: shown. in Figs. 5 to 8 and L1, there are no springs between the bottom of cylinder 47; I shall now. describe this form of. the invention- The cylinderhead '11, valve 12, stem 13, and push rod 18 arearranged aszbefore. The rocker arm 4B'inthis instance is provided with a shaft 49, shouldered at each end to accommodate the saddle portions 50 of cylinder 47. This cylinder is guided on piston 51, held just as piston 25, on the lower surface of a bracket 52. This bracket has depending sides 53. Since cylinder 47 (as shown most clearly in Fig. 8) has a rectangular outline, it can also be guided by these sides 53. If necessary, a supplemental guide pin 54 can also be provided. Adjacent each end of the cylinder 47 there is a hole 55'for the accommodation of the compression springs 56. These springs act against the bottom of bracket 52 and serve the same purpose as 'spring'26 of Fig. 1.

In other respects the device is similar to that illustrated in Figs. 1 to 4. The packing ring 57 is, however, shown as permanently fastened to the bottom of piston 51, as by the aid of the metal plate or ring 58.

In this form of the invention, the channel structure 52+53 may extend the whole length of the engine, as best shown in Figure 11 and all of the cylinder mechanisms 47-51 can be supported thereon.

In the form of my invention illustrated in Figs. 9 and 10, it is the piston rather than the cylinder which is movable. In this form, I show a rocker arm 59 having a shaft 60, with reduced ends 61. In this instance, each of these ends is controlled by its own dash pot mechanism. Thus straddling the left hand end 61 is a piston 62; and a corresponding piston 63 straddles the right hand end 61. Each of these pistons works in a stationary cylinder, such as 64 and 65. In the present instance, these cylinders are integral with a support 66, having a longitudinal aperture 67 communicating with all the cylinders through ,tapered apertures 68. A compression spring 69, surrounds each cylinder 64, and is confined by the lower surface of. support 66 and a flange 70 on the piston 62. This spring acts in a manner equivalent to spring 26, and serves to urge the telescoping parts apart.

When rocker 59 is operated toopen valve 12, the fluid in space 71 is forced by upward movement of piston 62 through the adjustable narrow space 72 formed between plug 73 and aperture 68. This plug 73 is adjustable just as plug '33, by the aid of a stud 74 threaded into support 66 above aperture 68. Downward or closing movement of piston 62 is substantially unretar'ded, because fluid can readily flow from aperture 67 through passageways 75, 76 in plug 73, into space 71. Valve 77 is unseated and uncovers aperture 76 due to the suction, when this downward movement takes place. This valve is urged to closing position by conical spring 78, resting at its bottom on packing ring 79. In

order to maintain the cylinder space 71 with sufficient liquid, a reservoir connecting to aperture 67 can be provided. I indicate such a reservoir diagrammatically at 80. I

The operation of this form of my invention is. substantially the same as of the forms already described. Downward movement of the axis of rocker 48 is substantially unopposed, springs 69 serving tourge the rocker arm into contact with the push rod 18 and valve stem 13. Upward movement is, however, very strong- 1y: resisted and buffed by the one way action of valve 77, so that the push rod 18 can serve to operate the valve.

I- claim:

I. In 'a valve actuating mechanism for. internal combustion engines, a rocker arm having an intermediate axis, a fluid piston and cylinder, one stationary, the other carrying a bearing for the arm adjacent the axis, means resiliently urging the cylinder and piston apart to vary the position of the axis, and a valve controlling a large passageway to permit ready ingress of fluid between the piston and the cylinder when they move apart, but closing the passageway when the piston and cylinder move together, thereby forcing fluid through another restricted passageway out of the space between the cylinder and piston.

2. The combination as set forth in claim 1 in which means are provided for forming the restricted passageway, including an axially adjustable member in the piston, for adjusting the size of the passageway.

3. The combination as set forth in claim 1, in which means are provided for forming the restricted passageway, including an adjustable tapered plug arranged in an axial aperture in the piston.

4. In a rocker arm support, a cylinder and a piston, one of said parts supporting the arm, said piston being hollow and provided with a tapered aperture, and a tapered plug in said aperture and adjustable to vary the passageway formed between it and the piston, whereby the degree of resistance to egress of fluid between the cylinder and piston can be adjusted.

5. The combination as set forth in claim 4, with the addition of means for resiliently urging the piston and cylinder apart, and means whereby a large passageway is opened to permit the resilient means to act rapidly.

6. In a valve actuating mechanism for internal combustion engines, a cylinder and a piston interposed in said mechanism, said piston being hollow and provided with a tapered aperture, and a tapered plug in said aperture and adjustable to vary the passageway formed between it and the piston, whereby the degree of resistance to egress of fluid between the cylinder and piston can be adjusted.

7. In a valve actuating mechanism for internal combustion engines, a cylinder and a piston interposed in said mechanism, said piston being hollow, the hollow space communicating with the space between the piston and the cylinder, a plug in the hollow space, having an opening therethrough and defining an annular space between it and the piston, and a valve for closing the opening in the plug, said valve being guided in the hollow piston, but of irregular outline to permit passage of fluid past the plug through the annular passageway.

8. In operating mechanism for valves and the like the combination of a support having a guide extending therefrom, a member slidably associated with said guide, a rocker arm, a bearing for the rocker arm carried by the slidable member, means yieldingly urging said member away from said guide, a passage extending through said support into the space between the guide and the member, and a plug arranged in said passage and spaced from the wallscthereof to provide a permanent vent.

9. In operating mechanism for valves and the like the combination of a support having a guide extending therefrom, a member slidably associated with said guide, a rocker arm, a'bearing for the rocker arm carried by the slidable member, means yieldingly urging said member away from said guide, a passage extending through said support into the space between the guide and the member, and a plug arranged in said passage and spaced from the walls thereof to provide a permanent vent, and said plug being provided with a valved inlet passage to admit fluid into the chamber.

101 In operating mechanism for valves and the like including a rocker member, the combination of a hollow support serving as a reservoir for oil, a pair of telescoping members extending from said support, one of said members carrying a bearing for said rocker, yielding means tending to separate said members to take up slack in the system, a passage leading from the interior of said support to the space between said members and a plug adjustably secured to said support and extending into said passage but spaced from the walls thereof to provide a permanent vent.

NELSON E. WOOLMAN. 

